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NASA NTRS1983

Outer planets satellites

The present investigation takes into account the published literature on outer planet satellites for 1979-1982. It is pointed out that all but three (the moon and the two Martian satellites) of the known planetary satellites are found in the outer solar system. Most of these are associated with the three regular satellite systems of Jupiter, Saturn, and Uranus. The largest satellites are Titan in the Saturn system and Ganymede and Callisto in the Jupiter system. Intermediate in size between Mercury and Mars, each has a diameter of about 5000 km. Presumably each has an internal composition about 60 percent rock and 40 ice, and each is differentiated with a dense core extending out about 75 percent of the distance to the surface, with a mantle of high-pressure ice and a crust of ordinary ice perhaps 100 km thick. Attention is also given to Io, Europa, the icy satellites of Saturn, the satellites of Uranus, the small satellites of Jupiter and Saturn, Triton and the Pluto system, and plans for future studies.

Morrison, D.↗

NASA NTRS1983

Energy and charge distribution of energetic helium ions in the outer radiation belt of the earth

The first direct measurement of the charge states of helium at energies greater than 0.5 MeV/nucleon in the outer radiation belt, obtained aboard the ISEE-1 spacecraft in 1977, is reported. High abundances of singly ionized helium, with He(+)/He(2+) = 0.4 + or - 0.1 at L = 3.3 was found during one perigee pass, with a sudden decrease of that ratio by a factor of about 10 between L = 3.3 and 3.7. It is shown that nonstationary and/or nonadiabatic processes may play an important role for the distribution of helium ions in the outer radiation belt.

Klecker, B.↗

NASA NTRS1984

Thermal ion composition measurements of the formation of the new outer plasmasphere and double plasmapause during storm recovery phase

Thermal ion composition measurements from several successive dusk sector passes by the DE-1 satellite show the formation of the new outer plasmasphere and double plasmapause following a sharp decrease in geomagnetic activity. In less than one day after the magnetic activity decrease, the outer plasmasphere formed and consisted of cold, essentially Maxwellian plasma with ion composition and thermal energy characteristics generally similar to those of the inner plasmasphere, albeit at significantly lower densities. There is also evidence that at times the thermal O(+) density is comparable to the H(+) density within the plasmasphere.

Horwitz, J. L.↗

NASA NTRS1984

Boundary layers of the earth's outer magnetosphere

The magnetospheric boundary layer and the plasma-sheet boundary layer are the primary boundary layers of the earth's outer magnetosphere. Recent satellite observations indicate that they provide for more than 50 percent of the plasma and energy transport in the outer magnetosphere although they constitute less than 5 percent by volume. Relative to the energy density in the source regions, plasma in the magnetospheric boundary layer is predominantly deenergized whereas plasma in the plasma-sheet boundary layer has been accelerated. The reconnection hypothesis continues to provide a useful framework for comparing data sampled in the highly dynamic magnetospheric environment. Observations of 'flux transfer events' and other detailed features near the boundaries have been recently interpreted in terms of nonsteady-state reconnection. Alternative hypotheses are also being investigated. More work needs to be done, both in theory and observation, to determine whether reconnection actually occurs in the magnetosphere and, if so, whether it is important for overall magnetospheric dynamics.

Eastman, T. E.↗

NASA NTRS1985

Interplanetary conditions during 3-kHz radio-wave detections in the outer heliosphere

Plasma waves detected by the Voyager 1 and 2 spacecraft beyond about 12 AU that may be associated with the turbulence expected at the heliopause are interpreted in terms of the characteristics of the interplanetary medium at large heliocentric distances. The low-energy charged-particle environment in the outer heliosphere during the observations of the unusual plasma-wave signals is addressed. The particle data suggest that the outer heliosphere was unusually stable and free of transient shock and particle events for the roughly eight months during the wave observations.

Lanzerotti, L. J.↗

NASA NTRS1985

The photochemistry of the atmospheres of the outer planets and their satellites

The thermal structure and composition of Uranus, Neptune, Saturn, Jupiter, Titan, and Io are described. Molecular hydrogen is the dominant constituent in the atmosphere of the outer planets. The hydrogen and helium, methane, ammonia and phosphine, and carbon monoxide photochemical reactions of the outer planets are studied. The importance of Jupiter's lightning as a source of organic matter is examined. The aerosol and haze layers of the stratosphere of Jupiter, Saturn, Neptune, and Uranus are observed. The photochemistry of Titan's atmosphere, which includes nitrogen, methane, carbon monoxide, and carbon dioxide reactions, is analyzed. The SO2 atmosphere on Io is discussed.

Strobel, D. F.↗

NASA NTRS1985

Wave observations in outer planet magnetospheres

The first measurements of plasma waves and wave-particle interactions in the magnetospheres of the outer planets were provided by instruments on Voyager 1 and 2. At Jupiter, the observations yielded new information on upstream electrons and ions, bow shock dissipation processes, trapped radio waves in the magnetospheres and extended Jovian magnetotail, pitch angle diffusion mechanisms and whistlers from atmospheric lightning. Many of these same emissions were detected at Saturn. In addition, the Voyager plasma wave instruments detected dust particles associated with the tenuous outer rings of Saturn as they impacted the spacecraft. Most of the plasma wave activity at Jupiter and Saturn is in the audio range, and recordings of the wave observations have been useful for analysis.

Scarf, F. L.↗

NASA NTRS1986

Performance analysis of a cascaded coding scheme with interleaved outer code

A cascaded coding scheme for a random error channel with a bit-error rate is analyzed. In this scheme, the inner code C sub 1 is an (n sub 1, m sub 1l) binary linear block code which is designed for simultaneous error correction and detection. The outer code C sub 2 is a linear block code with symbols from the Galois field GF (2 sup l) which is designed for correcting both symbol errors and erasures, and is interleaved with a degree m sub 1. A procedure for computing the probability of a correct decoding is presented and an upper bound on the probability of a decoding error is derived. The bound provides much better results than the previous bound for a cascaded coding scheme with an interleaved outer code. Example schemes with inner codes ranging from high rates to very low rates are evaluated. Several schemes provide extremely high reliability even for very high bit-error rates say 10 to the -1 to 10 to the -2 power.

Lin, S.↗

NASA NTRS1986

Strategy for exploration of the outer planets: 1986-1996

Over the past decade COMPLEX has published three strategy reports which, taken together, encompass the entire planetary system and recommend a coherent program of planetary exploration. The highest priority for outer planet exploration during the next decade is intensive study of Saturn (the planet, satellites, rings, and magnetosphere) as a system. The Committee additionally recommends that NASA engage in the following supporting activities: increased support of laboratory and theoretical studies; pursuit of earth-based and earth-orbital observations; commitment to continued operation of productive spacecraft; implementation of the instrument development plan as appropriate for the outer solar system; studies of deep atmospheric probes; development of penetrators or other hard landers; development of radiation-hardened spacecraft; and development of low-thrust propulsion systems. Longer-term objectives include exploration and intensive study of: the Uranus and Neptune systems; planetology of the Galilean satellites and Titan; and the inner Jovian system.

Source record↗

NASA NTRS1986

Statistical study of enhanced ion fluxes in the outer plasmasphere

DE-1 measurements of ion outflows at E = 5 eV to 32 keV in the Northern Hemisphere outer plasmasphere are compiled in graphs and investigated statistically. The data comprise 40 dayside (6:00-12:00 magnetic local time) and 50 nightside (18:00-23:00) passages at magnetic activities Kp = 0-7 and include six magnetic storms and recoveries as well as quiet periods. Features noted include enhanced number fluxes during periods of increased magnetic activity, upward dayside and downward nightside flows, peak net H(+) fluxes greater than 10 to the 8th/sq cm sec, and greater field-aligned flows (but at lower ion temperatures) in the outer plasmasphere than in the plasma trough.

Menietti, J. D.↗

NASA NTRS1987

Star formation in outer galaxy molecular clouds

The characteristics of 50 molecular clouds outside the solar circle (mostly around the radius of 14 kpc) were studied using the NRAO telescope. Maps of CO (J = 1 to 0), (C-13)O, and CO (J = 2 to 1) emission were constructed. The cloud sizes (several tens of pc in length) and masses (up to the several-hundred-thousand solar mass range) are typical of GMCs. The cloud envelope kinetic temperatures are significantly lower (about 7 K) than those typical for GMCs in the inner Galaxy; this is explained by a lower cosmic ray heating rate in the outer Galaxy. Radio data (obtained by the NRAO VLA at 6 and 20 cm) and far-IR observations (made from the Kuiper Airborne Observatory) yield evidence for newly formed late O and early B stars in the outer-Galaxy clouds.

Kutner, Marc L.↗

NASA NTRS1988

Long-Lived Glass Mirrors For Outer Space

Paper summarizes available knowledge about glass mirrors for use in outer space. Strengths and weaknesses of various types of first and second reflective surfaces identified. Second-surface glass mirrors used in outer space designed to different criteria more stringent for terrestrial mirrors. Protons, electrons, cosmic rays, meteorites, and orbiting space debris affect longevities of components. Contamination also factor in space.

Bouquet, Frank L.↗

NASA NTRS1987

Outer magnetospheric fluctuations and pulsar timing noise

The Cheng, Ho, and Ruderman (1986) outer-magnetosphere gap model was used to investigate the stability of Crab-type outer magnetosphere gaps for pulsars having the parameter (Omega-square B) similar to that of the Crab pulsar. The Lamb, Pines, and Shaham (1978) fluctuating magnetosphere noise model was applied to the Crab pulsar to examine the type of the equation of state that best describes the structure of the neutron star. The noise model was also applied to other pulsars, and the theoretical results were compared with observational data. The results of the comparison are consistent with the stiff equation of state, as suggested by the vortex creep model of the neutron star interior. The timing-noise observations also contribute to the evidence for the existence of superfluid in the core of the neutron star.

Cheng, K. S.↗

NASA NTRS1987

Enhanced low energy (1 MeV) ion fluxes in the outer heliosphere

The Low Energy Charged Particle (LECP) experiment on the Voyager 2 spacecraft in the outer heliosphere (greater than 10 AU) has observed several occasions when there was a peak in the interplanetary ion spectra for ions of energies of about 0.5-1.0 MeV. Such enhancements can last for several days, suggesting that at these times particles of these energies dominate the low energy cosmic population in this region of the heliosphere. Two specific cases are discussed. The enhancements seem to be associated with the passage of transient interplanetary shock events, with the ion anisotropies generally showing outflow. The most straight-forward explanation for the observations seems to involve only a propagation effect of ions from the inner to the outer solar system. This conclusion is supported by simple modeling of the propagation of an event observed at 1 AU to the spacecraft at about 12 AU.

Gold, R. E.↗

NASA NTRS1987

Neutral upper atmospheres of the outer planets

The major characteristics of the neutral upper atmospheres of outer planets are discussed, with special attention given to the Uranus upper atmosphere, probed by Voyager 2. The composition, thermal structure, photochemistry, and vertical mixing of the Uranus atmosphere are compared with the respective features of other outer planets. Unlike the atmospheres of Jupiter and Saturn, which reflect the solar ratios of the elements, the Uranus atmosphere was found to have only few constituents, including NH3, CH4, H2, He, C2H2, and C2H6. The eddy diffusion coefficient of Uranus, determined from occultation experiments, was found to be in the range 10,000-100,000 sq cm/sec, the lowest value amongst the major planets; this implies relatively sluggish vertical mixing. Another major difference from Saturn and Jupiter is in the fact that stable hydrocarbon products (C2H2 and C2H6) in the Uranus atmosphere begin to condense at around 5-10 mb level, resulting in the production of haze in the lower stratosphere.

Atreya, S. K.↗

NASA NTRS1988

Possible explanations of north-south plasma flow in the outer heliosphere and meridional transport of magnetic flux

Observed meridional plasma flow and its connection with other plasma parameters in the outer heliosphere are discussed. The dynamics of the flow are examined locally and compared with observed plasma parameters and a global flow model which predicts such flows in a steady solar wind. The observational evidence supports stream dynamics and associated pressure gradients as responsible for driving the flow. Such a meridional flow may result in a net transport of magnetic flux from regions near the heliographic equator. The amplitude of the observed meridional component of solar wind flow is consistent with observed magnetic flux deficits in the outer heliosphere. The limited coverage of heliographic latitude by Voyager 2 precludes a direct measurement of the full flow pattern; however, the magnitude of reported magnetic flux deficits and the unambiguous, regular variations in the meridional flow suggest that the stream interactions do produce a net movement of magnetic flux away from the heliographic equator.

Mcnutt, R. L., Jr.↗

NASA NTRS1988

Outer atmospheric research - One tether capability

One specific tether application of far-reaching promise would be to conduct outer atmospheric research by using a tethered subsatellite deployed downward from an orbiting 'mother' craft such as the Shuttle Orbiter. This capability would gather scientific and engineering/technology information about the outer atmosphere, primarily from 150 km down to perhaps 90 km. This paper presents current determinations of specific user needs, tether capabilities, and technological and program requirements to fulfill this application of tethers in space.

Anderson, John L.↗

NASA NTRS1989

Recurrent solar wind structures in the outer heliosphere

The paper presents recent work on evolution of recurrent solar wind structures in the outer heliosphere. Corotating shocks, corotating interaction regions, and merged interaction regions are studied, and an MHD simulation model in which the jump conditions at all shock crossings satisfy the Rankine-Hugoniot solution is examined. Simulation results which describe the evolution of idealized recurrent solar wind structures between 14 AU and the termination shock are reported which show that merged interaction regions belonging to two to four consecutive solar rotations coalesce with each other between 30 AU and the termination shock to reshape the heliospheric structures. In the outer heliosphere, forward and reverse interplanetary shocks which continuously heat the solar wind plasma are investigated.

Whang, Y. C.↗